The present invention relates to a pack for loading a plurality of so-called "instant photographing films" (self-processing film units which are hereinafter referred to merely as "units" when applicable) piled one on another for use in an instant camera. More particularly, the invention relates to a pack wherein exposed units can be successively pulled out of the pack while the developing solution in each unit (hereinafter referred to as "processing solution") is uniformly spread in a predetermined image forming region of the unit.
A product composed of the units and the pack of the general type referred to herein is commercially available, for instance, as instant film type No. PR-10 manufactured by Eastman Kodak Co. The arrangement of the essential components of the units and pack of this type is shown in FIGS. 1 and 2.
As shown in FIG. 1, the unit 10 includes a first flexible sheet 1 having an image receiving layer, a second flexible sheet 2 for assisting the uniform spreading of the processing solution over an image forming region 6 to a predetermined thickness, and a bonding member 3 which is an intermediate sheet or an adhesive tape. The bonding member 3 is interposed between the two sheets 1 and 2 to form them into one unit.
The first and second sheets 1 and 2 have a container 4 and a trap 5, respectively. The container 4 is adapted to hold the processing solution along the front edge of the unit and it is tearable so that, upon application of an external pressure higher than a certain value, the processing solution is spread between the sheets 1 and 2. The trap 5 is adapted to catch surplus processing solution which is discharged from the container 4. The trap 5 is provided along the rear edge of the unit.
Compared with the thickness of a portion of the unit formed by the sheets 1 and 2 and the bonding member 3, for instance, the thickness of the image forming region 6, the thickness of the container 4 or the trap 5 is relatively large, usually 1.3 to 1.5 mm.
The pack 20 is a relatively flat box-shaped case, as shown in FIG. 2. The pack 20 has an upper plate 21 in which an exposure opening 22 is formed and a front side plate 23 in which an elongated outlet 24 is formed so that the unit 10 can pass therethrough.
A plurality (usually ten) of units 10 piled one on another are inserted in the pack 20 with the container sides adjacent the outlet 24. The units 10 are supported by a leaf spring 25 in such a manner that they are depressed towards the opening 22 and the image forming region 6 of the uppermost unit 10 is in alignment with the opening 22.
The pack 20 containing the units 10 as described above is loaded in the camera. When the uppermost unit 10 is exposed, a pushing pawl (not shown) provided in the camera moves towards the exposure opening 22 in the direction of the arrow A from the rear side of the pack along a groove 26 formed in the pack 20 so that the top end of the pawl abuts against the rear edge of the uppermost unit 10 thereby to push a part of the uppermost unit 10 out of the outlet 24 of the pack 20.
When a part of the unit 10 including the container 4 and a part of the image forming region 6 is moved to the nip point of a pair of developing rollers 27 and 28 which form a part of the camera, the unit 10 is completely moved outside the pack 20 by the force of the pair of developing rollers 27 and 28 which rotate respectively counterclockwise and clockwise. As a result, the unit 10, guided at a predetermined angle .theta. (12.degree. to 18.degree.) slightly upwardly toward the photographed object by the rollers, is discharged from the camera.
As the unit 10 is pressurized by the developing rollers 27 and 28 continuously from the container 4 to the trap 5, the container 4 is burst and the processing solution is spread between the sheets 1 and 2 to perform developing in the image forming region 6.
Specific features of the arrangement of the outlet 24 of the pack 20 and the relative position of the outlet 24 and the pair of developing rollers 27 and 28 on the camera side will be described in more detail.
The pair of rollers 27 and 28 will be referred to as "a slave roller 27" and "a master roller 28". Each of the rollers has a diameter of about 9 to 10 mm and the rollers are arranged parallel to one another. The master roller 28 rotates counterclockwise on a fixed axis. The slave roller 27 is provided above the master roller 28 with a small gap d between the two rollers. The slave roller 27 is rotated clockwise. Further, the slave roller 27 has a suspension device, namely, a spring 29 so that its axis is movable vertically. The two rollers 27 and 28 thus constructed are arranged in front of the outlet 24 of the pack 20 (on the left-hand side in FIG. 3).
The loading position of the pack 20 is set so that the outer surface 23a of the front plate 23 is about 6 mm away from the axis C of the master roller 28. A sloped surface 30 which inclines inwardly of the pack 20 is formed on the upper edge of the front side plate 23 which forms a part of the outlet 24 extending in the longitudinal direction of the outlet 24 so that the unit 10 can be smoothly moved out of the pack 20. The width D of the opening between the lower surface 21b of the upper plate 21 and the edge 31 which is the outer edge of the sloped surface 30 is set at about 1.4 mm.
The edge 31 of the outlet 24 is spaced about 0.35 mm away from the outer wall level B of the master roller in the opposite direction to the object. That is, there is a level difference E between the outer wall level B and the edge 31. The outer wall level B is the level of the generating line forming the cylindrical wall of the roller 28, which is the closest to the cylindrical wall of the slave roller 27 and is perpendicular to the exposure system optical axis of the camera.
Both ends of the edge 31 of the outlet 24 merge with slopes 32 each having a gradient of about 1/10 so that the degree of contact with the unit 10 gradually decreases towards the edge portions of the unit.
Due to ambient temperature variations when the units 10 are inserted in the pack 20 or developed, a variation in the number of the units 10 in the pack 20, or mechanical differences of the camera with which the pack are used, sometimes the processing solution is spread with a non-uniform thickness which is harmful to the quality of picture. Especially in the first and last units of the pack 20, non-uniform spreading can occur. A typical percentage of the processing solution spread variation is from 10% to 20%.
When non-uniform spreading occurs, the quantity of processing solution, which should be caught by the trap 5 of the unit 10, may be insufficient or there may be too much. Therefore, sometimes the processing solution may leak out of the unit 10 or may be spread in such a manner that the front of the processing solution is partially wavy in the widthwise direction of the unit 10 thus adversely affecting the picture density and the color balance.